Pressure reducing devices in particular for carburation systems



Oct. 30, 196 A. L. MENNESSON 3,061,286

PRESSURE REDUCING DEVICES IN PARTICULAR FOR CARBURATION SYSTEMS ,FiledJan. 24, 1961 /\/v/v TOR ANDRE LOU/5 MENMFSSON United States Patent()fiice 3,051,285 Patented Oct. 30, 1962 3,061,286 PRESSURE REDUCINGDEVICES IN PARTICULAR FOR CARBURATION SYSTEMS Andr Louis Mennesson,Neuilly-sur-Seine, France, as-

signor to Soeiete Industrieile dc Brevets et dEtudes S.I.B.E.,Neuilly-sur-Seiue, France Filed Jan. 24, 1961, Ser. No. 84,693 Claimspriority, application Franc-e Jan. 28, 1%0 3 Ciaims. (Cl. 261-36) Thepresent invention relates to pressure reducing devices especially foruse in carburation systems working normally by continuous injection offuel through at least one fuel injection orifice opening into the airintake pipe of the system-downstream of the throttleprovided in saidpipe.

Such carburation systems comprise a pressure reducing device interposedbetween a source of fuel under pressure and said injection orifice so asto reduce to a value suitable for injection through said orifice thepressure of the liquid supplied by said source.

The pressure reducing device comprises a chamber having an inlet fedfrom said source, an outlet leading to said injection orifice and aby-pass port controlled by a by-pass valve having an active portionextending across said port to control the outflow of fuel therethroughin such manner as to reduce the fuel pressure in said chamber to thedesired value. This by-pass valve is subjected to the opposed actions ofthe fuel pressure in said chamber tending to open said valve and of amovable member tending to close said valve, this member being actuated,in a direction coinciding with the direction of movement of said valve,by control means, responsive to vari ations of a factor of operation ofthe engine. Generally said control means are diaphragm means carryingsaid member and subjected to the action of a pressure which constitutesthe above mentioned factor of operation of the engine, this pressurebeing that existing in a venturi located in the carburetor air intakepipe upstream of the throttle. Said control means are operativelyconnected to said movable member at points located in an annular regionthereof transverse to the above mentioned direction.

In pressure reducing devices of this type such as known up to now, thepressure obtained at the outlet is not quite accurately determinedbecause undesirable frictions occur in the transmission of the action ofsaid control means to said by-pass valve.

The object of the present invention is to provide a pressure reducingdevice which obviates this drawback.

For this purpose, according to the invention, the action of the movablemember is transmitted to the by-pass valve exclusively by a push-rodbearing at its ends respectively against said valve and against saidmovable member, the length of said rod being greater than the distancebetween said valve active portion and said annular region of saidmember, said valve and said member being shaped to accommodate saidpush-rod so that the only contact of said rod with said valve is on theother side of said valve active portion from said member and the onlycontact of said rod with said member is on the other side of said memberannular region from said valve.

A preferred embodiment of the present invention will be hereinafterdescribed, with reference to the accompanying drawings, given merely byway of example and in which:

FIG. 1 is an axial sectional view of a carburation system comprising apressure reducing device according to this invention;

FIGS. 2 and 3 are diagrammatical views of known devices given toindicate the drawbacks obviated by the present invention.

The carburation system shown by FIG. 1 comprises an intake pipe 22through which air supplied through an air filter 33 flows in thedownward direction. This pipe 22 is provided, upstream of an airthrottle 23, with'a venturi 24 for measuring the flow rate of the airsucked in by the engine. In order to increase sensitivity, a secondventuri 25 is disposed inside venturi 24, coaxially therewith. A conduit15 opens into the throat of venturi 25.

Fuel is injected through calibrated orifice 11 into pipe 22 at a pointthereof downstream of throttle 23. This orifice 11 opens into a chamber26 fed with air through a duct 27 and in which the pressure is close toatmospheric pressure. This chamber 26 opens into intake pipe 22 throughan orifice 28 the cross section area of which is smaller as comparedwith that of duct 27 so that orifice 11 is not subjected to the suctionwhich may exist in pipe 22 downstream of throttle 23.

Fuel is supplied to orifice 11 from a pump 8 which delivers this fuel ata pressure higher than the desired pressure to be obtained at saidorifice 11.

The pressure reducing device with which the present invention isconcerned is interposed between the delivery conduit 6 of pump 8 and aconduit 10 leading to injection orifice 11 to supply this orifice withfuel at the desired pressure.

This pressure reducing device comprises a cylindrical casing 1 forming achamber 2 having, at its lower part, on the one hand, an inletcommunicating with the pump delivery conduit 6 through a calibratedmetering orifice 7 and on the other hand, an outlet communicating withconduit 10 which leads to injection orifice 11.

Chamber 2 is open at the top to form a by-pass port the degree ofopening of which is controlled by a by-pass valve 3 and through which anexcess of fuel flows out into a body 12 to return therefrom through aconduit 13 to the fuel tank 9 serving to feed pump 8. Bypass valve 3comprises, at the top thereof, an active portion in the form of anannular disc cooperating with the edge of the by-pass port formed at thetop of chamber 2. Bypass valve 3 further comprises a stem 4 extendingdownwardly from said active portion and slidably guided in a sleeve 5integral with casing 1 and coaxial therewith.

The pressure in chamber 2, and therefore the pressure at which fuel isfed through the outlet conduit 10, depends upon the degree of opening ofby-pass valve 3. This valve is urged upwardly by the fuel pressure inchamber 2 and downwardly by a push-rod 18 operated as it will behereinafter explained. The force with which rod 18 pushes valve 3downwardly therefore determines the pressure at the outlet 16 of chamber2.

The force acting on push-rod 18 is exerted by a diaphragm 14 itselfsubjected to the suction transmitted thereto through conduit 15 whichopens into the throat of venturi 25. In order to prevent this suctionfrom acting upon valve 3, there is interposed between said valve anddiaphragm 14 a second gas-tight diaphragm 16 of an area substantiallysmaller than that of diaphragm 14. A member 17 is carried by the centralportions of these diaphragms 14 and 16 so that said member is movable ina direction coinciding, at least approximately, with the direction ofthe displacements of valve 3. In view of the difference between theareas of diaphragms 14 and 16, a suction transmitted through conduit 15to the space between said diaphragms produces a downward displacement ofmember 17. As said member is connected with valve 3 through rod 18, thissuction constitutes the factor of operation which determines the forcewith which valve 3 is urged downwardly and therefore the pressure of thefuel fed at the outlet 10 of chamber 2 of the pressure reducing device.

Now, in view of the fact that obviously all causes of friction betweenparts of the device should be avoided, the obvious arrangement is thatillustrated by FIG. 2 where rod 18, of a length just a little smallerthan the distance between diaphragm 16 and the disc portion of valve 3bears directly at its ends upon said parts 17 and 3, respectively.

Such an arrangement indeed eliminates frictions as would exist if thetransmission included hinges, but it introduces another cause offriction which will be explained with reference to FIG. 3. The suctionforces acting on diaphragms 14 and 16 have a resultant f the point ofapplication of which is A, located substantially in the plane Q ofdiaphragm 14. At point B where rod 18 is in contact with member 17, areaction force, equal and opposed to f, is exerted by rod 18 on member17. In a likewise manner, the fuel pressure applies an upward force f onvalve disc 3 at point thereof located at the center of the under face ofsaid disc 3 (the plane of this face being designated by P), and at pointD where rod 18 is bearing upon valve 3 a reaction force equal andopposed to f is exerted by said rod 18 upon valve 3.

If valve 3 and member 17 constantly remained perfectly in line with eachother, there would be no trouble. But in practice this is impossible andthe two couples of forces (f and the corresponding reaction force, f andthe corresponding reaction force) brought into play tend to produce themaximum possible misalinement between the axis of piece 17, the axis ofpush-rod 18 and the axis of the stem 4 of valve 3. The consequences arefrictions, in particular between valve stem 4 and its guiding sleeve 5,and strains in diaphragms 14 and 16, which are distorted. Thus thepressure reducing device lrses most of its sensitivity because thefrictions and strains due to the above mentioned misalinement areconsiderable in regard of the accuracy to be obtained from the device.

In order to obviate this drawback, according to the present invention,valve 3 (with its stem 4), member 17 and push-rod 18 are arranged insuch manner that said rod 18 bears against valve 3 only at a pointlocated on the other side of plane P from member 17 and that said rod 18bears against member 17 only at a point located on the other side ofplane Q from valve 3.

For this purpose, the stem 4 of valve 3 is provided with an axial blindhole 19 extending downwardly from plane P and piece 17 is provided withan axial blind hole 20 extending upwardly from the lower end of saidpiece 17 to some distance above plane Q, and push-rod 18 is of a lengthgreater than the distance between planes P and Q so that the ends ofsaid rods bear respectively against the bottoms 19,, and 20 of theseholes 19 and 20.

Thus each of the above mentioned couples of forces (f and thecorresponding reaction force on the one hand and f and the correspondingreaction force on the other hand), instead of tending to increasemisalinement between parts 17, 18 and 3, tends on the contrary tomaintain alinement. Any risk of increased friction between valve stem 4and its guide 5 and of distortion of diaphragms 14 and 16 is thuseliminated.

Holes 19 and 20 are made of slightly greater diameters than therespective portions of rod 18 engaged therein. Furthermore the bottomsurfaces 19 and 20,, and the ends of rod 18 are made of curved axialsection, the radius of curvature of each rod end being smaller than theradius of curvature of the corresponding bottom surface 19,, or 20,.

Preferably, as shown, a spring 21 is interposed between the bottom ofchamber 2 and the annular disc portion of valve 3 so as to balance theweight of the movable structure actuated by diaphragms 14 and 16.

Owing to this spring, valve 3 is in wide open position when no suctionis transmitted through conduit 15, i.e. when the pressure on both sidesof diaphragm 14 is the atmospheric pressure. The relative pressure inoutlet conduit 10 is then zero and there is no fuel injection, which iscorrect since there is no air fiow through intake pipe 22. On thecontrary, if there was not a spring such as 21, the sensitivity of thedevice would produce a small relative pressure in outlet conduit 10 andfuel would be injected at 11 into intake pipe 22.

In order to protect diaphragm 14, a cover 29 is provided above it andthe chamber 30 formed between said diaphragm 14 and cover 2? is placedin communication with the atmosphere through a hole 31, either directlyor preferably through a conduit 32 opening into intake pipe 22 justdownstream of air filter 33.

In a general manner while the above description discloses a preferredembodiment of the invention, it should be well understood that saidinvention is not limited to this embodiment as there might be changesmade in the arrangement, disposition and form of the parts withoutdeparting from the principle of said invention as comprehended withinthe scope of the appended claims.

What I claim is:

1. For use in connection with a carburation system comprising an airintake pipe, a throttle in said pipe, a fuel injection orifice openinginto said pipe downstream of said throttle, a venturi in said pipeupstream of said throttle, and a fuel pump for delivering fuel underpressure, a pressure reducing device for lowering the fuel pressuresupplied by said pump to a value suitable for fuel injection throughsaid orifice, which pressure reducing device comprises, in combination,a body, means in said body forming a vertical axis cylindrical chamber,said chamber having, at the bottom thereof, an inlet connect ed with thedelivery of said fuel pump and an outlet con nected with said fuelinjection orifice, said chamber being open at the top to form a circularupper edge, a by-pass valve having a top portion in the form of a discextending over said edge to control the gap between said edge and saiddisc, said valve further comprising a stern extending downwardly fromsaid disc coaxially therewith, means in said chamber for guiding saidvalve stem coaxial with said chamber, a member in the form of a body ofrevolution about its axis, two horizontal annular diaphragms disposedone above the other in said body, said diaphragms having their outerperipheries fixed to said body above said chamber and their innerperipheries fixed to said member to hold it with its axis in line withthe axis of said chamber, the upper diaphragm having an area greaterthan that of the lower one, conduit means for connecting the spacebetween said two diaphragms with the throat of said venturi, said valvestem being provided with a blind hole extending axially therein from thetop of said valve disc to some distance below it, said member beingprovided with a blind hole extending axially therein from the bottom endthereof to some distance above the plane of the upper diaphragm, and apush-rod of a length greater than the distance between said valve discand the upper diaphragm, said rod having its ends applied respectivelyagainst the bottoms of said blind holes and being otherwise out ofcontact with said valve and said member.

2. A pressure reducing device according to claim 1 3,061,286 5 6 inwhich the ends of said rod are rounded and the bot- References Cited inthe file of this patent toms of said holes are of curved concave shape,the radius of curvature of each rod end being smaller than UNITED STATESPATENTS that of the hole bottom against which it is bearing. 2,715,009Beekley Aug. 9, 1955 3. A pressure reducing device according to claim 15 2,389,849 Shohan June 9, 1959 further comprising a spring interposedbetween the bot- 2,943,849 Csecs July 5, 1960 tom of said chamber andthe disc portion or said by-pass 2,977,948 Kittler Apr. 4, 1961 valve,this spring being capable of balancing the total 2,992,643 Ball July 18,1961 Weight of the movable structure consisting of said valve, 2,998,232Mennesson Aug. 29, 1961 said stem and said member. 10 3,009,794 BarfodNov. 21, 1961

